题目内容

【题目】下列可以组成经线圈的是(  )
A.东经10°和西经80°
B.东经90°和西经90°
C.东经120°和东经60°
D.西经10°和西经170°

【答案】B
【解析】在地球仪上,经线是连接南北两极并且与纬线垂直相交的半圆,经度的划分是以0°经线为界,向东向西各分了180°,向东的180°称东经,用符号“E”表示,向西的180°称西经,用符号“W”表示;经线的形状是半圆,每条经线与它相对的经线组成一个经线圈,其度数和为180°,东西经度相反(0°经线和180°经线相反).比较题干中的四个选项可得,符合“之和是180°,一条是东经度数,另一条则是西经度数”的两条经线是东经90°和西经90°,此两条经线能组成经线圈.故选:B.

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【题目】阅读下面短文,用括号内所给动词的适当形式填空(必更时可加情态动词或助动词)

If you've ever stayed up late and then gotten up early the next day, you know what it's like not to get enough sleep. It's very uncomfortable feeling. In fact, for many years scientists 1(believe) that sleep is like food - if we don’t get enough of it, we might get sick or even die. But now they 2 (start)to wonder just how much sleep we need.

Researchers at Imperial College London did a study on fruit flies(果蝇). They found that flies that slept for very short periods of time - about72 minutes a day -still 3 (live) about as long as flies that slept for normal amounts of time. One of the female slept for just 4 minutes each day on average. This has led the researchers to wonder if sleep is less necessary than we previously thought.

Humans are very different from fruit flies. Sleep 4(help) repair tissue (组织) when our bodies perform a lot of maintenance (维护). Sleeping allows our bodies 5 (get) well again from the stress we experience each day. But can we really die from not sleeping? No humans have died so far from 6 (stay) awake for too long. The current(现在的)world record for sleeplessness 7 (hold) by Randy Gardner from the US, who stayed awake for 11 days and 25 minutes in 1964.

Scientist have not yet found any animals that don’t sleep at all. Even animals that only sleep for short periods are not completely sleepless.

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